The production of linear or cross-linked aqueous polyurethane-urea dispersions is known. The aqueous polyurethane-urea dispersions may be used for a wide range of commercial applications such as adhesives or coatings for various substrates including textile fabrics, plastic, wood, glass fibers and metals. Chemical resistance, abrasion resistance, toughness, tensile strength, elasticity and durability are among the many desirable properties of these coatings.
It has been disclosed in U.S. Pat. Nos. 5,041,494, 5,354,808 and 5,554,856, and also in copending applications, U.S. Ser. Nos. 08/992,163 and 08/992,551, that the properties of these dispersions can be improved by the incorporation of alkoxysilane groups into the polyurethane-ureas. However, regardless of the property level which may be obtained for coatings prepared from these polyurethane-urea dispersions, there is always a further need to increase certain properties, in particular solvent resistance.
Accordingly, It is an object of the present invention to provide aqueous polyurethane/urea dispersions which can be used to prepare coatings which possess improved solvent resistance and still retain the other valuable properties of aqueous polyurethane dispersions.
This object may be achieved in accordance with the present invention by blending aqueous dispersions of polyurethane/ureas containing alkoxysilane groups with colloidal silica.